avc_utils: skip empty NALs from malformed bistreams

    const uint8_t *nalStart;

    size_t nalSize;

    while (getNextNALUnit(&data, &size, &nalStart, &nalSize, true) == OK) {

        CHECK_GT(nalSize, 0u);

        if (nalSize == 0u) {

            ALOGW("skipping empty nal unit from potentially malformed bitstream");

            continue;

        }

        unsigned nalType = nalStart[0] & 0x1f;